Disposable diaper having stress relaxing structures and fasteners positioned for improved fit

Abstract

A disposable diaper comprises an absorbent part, a pair of ear parts projecting in opposite directions from the opposite side edges of one longitudinal end portion of the absorbent part, respectively, and two fastening means attached to the side edges of the ear parts, respectively. Each side edge has a first side edge section and a second side edge section, each ear part has a stress relaxing structure, in which a tensile stress smaller than that which is induced in the peripheral portion of the ear part is induced, in a portion thereof other than the peripheral portion, and each fastening means is attached to the ear part in a pulling section of the side edge, overlapping at least part of a first side edge section and part of a second side edge section so that component tensile forces of a tensile force applied to the fastening means are distributed at a desired distribution ratio to the waist lapping portion and the leg lapping portion of the absorbent part.

What is claimed is:  
     
       1. A disposable diaper comprising: 
       (a) an absorbent part formed by sandwiching an absorbent core between a topsheet and a backsheet, and having a first longitudinal edge and a second longitudinal edge;  
       (b) a pair of ear parts projecting laterally in opposite directions from said longitudinal edges, each said ear part having  
       i) a side edge being generally parallel to said longitudinal edge,  
       ii) an upper edge being generally perpendicular to said longitudinal edge,  
       iii) a lower edge being nonparallel to said upper edge,  
       iv) a stress relaxing structure extending laterally from said longitudinal edge, said stress relaxing structure being stretchable under a tensile force applied to said ear part and being capable of intercepting the transmission of said tensile force to said absorbent part,  
       v) a first boundary line extending from said side edge to said upper edge, tangentially to said stress relaxing structure,  
       vi) a waist lapping portion fastening component force distributing area being bounded by said first boundary line, said upper edge, and said side edge,  
       vii) a first side edge section extending along said side edge and forming said waist fastening component force distributing area,  
       viii) a second boundary line extending from said side edge to a point of intersection of said lower edge and said longitudinal edge, tangentially to said stress relaxing structure,  
       ix) a leg lapping portion fastening component force distributing area being bounded by said second boundary line, said lower edge, and said side edge,  
       x) a second edge section extending along said side edge and forming said leg fastening component force distributing area; and  
       xi) a peripheral portion including said waist and said leg lapping portion fastening component force distributing areas, said waist and said leg lapping portion fastening component force distributing areas surrounding said stress relaxing structure, said peripheral portion being virtually unstretchable under said tensile force, and  
       (c) a pair of fasteners, each said fastener being attached to said side edge of one of said ear part and overlapping at least part of said first side edge section and said second side edge section.  
     
     
       2. A disposable diaper according to claim  1 , wherein said stress relaxing structure has a substantially trapezoidal shape. 
     
     
       3. A disposable diaper according to claim  2 , wherein said lower edge of said stress relaxing structure is arcuate. 
     
     
       4. A disposable diaper according to claim  1 , wherein said stress relaxing structure forms a part of an ellipse or a part of a circle. 
     
     
       5. A disposable diaper according to claim  4 , wherein said lower edge of said stress relaxing structure is arcuate. 
     
     
       6. A disposable diaper according to any of claims  2 ,  3 ,  4 , or  5 , wherein said stress relaxing structure has a plurality of undeformed sections, a plurality of permanently deformed sections, and transitional sections between said undeformed sections and said permanently deformed sections. 
     
     
       7. A disposable diaper according to claim  1 , wherein said stress relaxing structure has a plurality of logitudinal slits. 
     
     
       8. A disposable diaper according to claim  7 , wherein said lower edge of said stress relaxing structure is arcuate. 
     
     
       9. A disposable diaper according to claim  1 , wherein said stress relaxing structure has at least one logitudinal slit. 
     
     
       10. A disposable diaper according to claim  9 , wherein said lower edge of said stress relaxing structure is arcuate.